Conventionally, elevators are equipped with a safety gear which is triggered by an overspeed governor. A common solution is such that when the elevator speed in the overspeed governor reaches a preset limit, the overspeed governor triggers the safety gear by means of the same rope that transmits the elevator speed to the overspeed governor. The structure and operation of an overspeed governor of this type is described in Finnish patent publication no. 76049.
In addition to gripping in an overspeed situation, situations occur in which the safety gear ought to be activated even if the elevator speed does not exceed the allowed limit. These situations include the testing of the safety gear in connection with the inspection of the elevator. For instance, certain elevators using a geared hoisting machinery cannot usually be accelerated to the gripping speed, requiring exceptional measures to allow the gripping function to be checked. Failure situations may also occur where it should be possible to stop the elevator independently of the hoisting machinery and the operating brake. A failure situation of this type is e.g. when an elevator starts from a floor with doors completely or partially open.
Another problem at present is that the overspeed governor has to be placed in a 10action where it can be accessed during inspection. If the elevator has a machine room, this is no problem, but in the case of other solutions regarding the machinery, when the overspeed governor is placed in the elevator shaft, a separate manhole is needed to permit the overspeed governor to be locked by way of exception in connection with inspection.